Rapid acting flame-retardant film emulsion drying solution



United States Patent RAPID ACTING FLAME-RETARDANT FILM EMULSION DRYING SOLUTION David Kaner, 2043 Coldwater Canyon Drive, Beverly Hills, Calif., and Patrick D. Dignan, Van Nuys, Calif. (5407 Satsuma Ave., North Hollywood, Calif.)

Our invention relates to a liquid desiccant and particularly to one for drying the gelatin emulsion of photographic film and the like.

Drying photographic films has been a time-consuming process, often employing natural evaporation in warm air cabinets, since the inception of the art. Attempts to reduce the time required by employing hot air have damaged the gelatin emulsion by causing it to melt to at least some degree and thus spoil the photograph. Another attempt has employed an alcohol. Gelatin has a greater afiinity for alcohol than for water, so the introduction of the former displaces the latter. However, alcohol is a well known flammable substance and when mixed with air is explosive. Still another attempt has been the air impingement process, which is accomplished by employing multiple jets of dry compressed air in a relatively large and expensive apparatus. This process reduces the normal drying time but is not rapid acting as herein defined.

Our rapid acting flame-retardant drying solution has a place throughout the photographic and allied industries, but it is particularly valuable with portable rapid film processing devices, such as employed for television newsreel work where extremely rapid processing of motion picture film is required. One such processing device is described in the co-pending patent application of P. Dignan for Film Processing Apparatus, Serial No. 512,697, filed June 2, 1955, which issued as Patents 2,810,- 332 and 2,810,572 on October 22, 1957. Since such apparatus may be located in any type of room, station wagon or airplane it is important that a drying agent be non-explosive and flame-retardant.

A suitable rapid drier must also accomplish the drying process without fogging the film, as is caused by excessive dehydration. This we have been able to accomplish, as well as attaining a flame retardant characteristic in our composition.

An object of our invention is to provide a flame-retard ant liquid for drying gelatin emulsions.

Another object is to provide such a liquid capable of drying film emulsions within one minute.

Another object is to provide a drying liquid that does not fog the film.

Another object is to provide a drying liquid that does not leave a residue, water marks or a scum on the film.

Another object is to increase the resistance of the film to scratching.

Another object is to prevent oil marks on the film caused by oil from the hands when the film is handled.

Broadly, our novel compound consists of approximately 77 parts of an alcohol and subsidiary substances, 13 parts of trichlorotrifiuoroethane and parts of distilled water, all by volume.

When passed through this liquid for about one minute and then squeegced out thereof photographic film is dried without streaks, watermarks or fogging in 30 seconds.

When the drying liquid is in the usual cell of a film processing machine, or in an ordinary teacup, for examice ple, the vapor therefrom will extinguish a lighted match with which one attempts to ignite the liquid. spilled on the floor, so that a small amount of the liquid is in contact with a considerable amount of air, it will burn with a small flame but will not explode.

If our drying liquid is exposed to air in the cell of a film processing machine or equivalent for long periods of time it will evaporate only gradually, such as 30% evaporated in two weeks. ,The anti-explosive and flame-retardant properties remain. This is very much different than for alcohol alone.

Our invention is described in greater detail in the following examples.

Example 1 Mix 38 parts of ethyl alcohol, 37 parts of isopropyl, 13 parts trichlorotrifiuoroethane, 10 parts distilled water and 2 parts triethanolamine, all by volume.

Certain variations of the above composition are permissible. The proportion of the alcohols as a group may vary from 50 to parts, the trichlorotrifluoroethane from 12 to 50 parts, the water from zero to 14 parts and the triethanolamine from zero to 4 parts.

In the above example the alcohol content dries the gelatin emulsion because of the greater affinity of gelatin for alcohol than for water. Trichlorotrifluoroethane has the formula CCl FCClF It is the anti-explosive and fiarne retardant ingredient. The water sets a lower limit to the dehydration of the gelatin. This prevents fogging by causing retention of at least 15 to 20% water in the gelatin as a minimum. The triethanolamine is a wetting agent and emulsion hardener, used to disperse water remaining on the surface of the film after treatment and thereby preventing water marks or streaks.

From the above variations of the composition preferred for commercial sale it is seen that other examples are possible; i.e.

Example 2 Mix 50 parts of ethel alcohol with 50 parts of trichlorotrifiuoroethane, by volume.

This will give a satisfactory dryer if the timing is accurately watched and correlated to the relative humidity and temperature of the air. The time required for drying is reduced from the usual 45 seconds to perhaps as little as 5 seconds. Error in timing will result in fogging the film. The anti-explosive and fiame-retardant properties are excellent. The use of a squeegee is recommended to achieve this rapid drying and to return excess liquid to the bath as a conservation measure.

Example 3 Mix 87 parts of ethyl alcohol with 13 parts of trichlorotrifluoroethane, by volume.

This gives a dryer having the drying characteristics of Example 2 with the minimum amount of trichlorotrifiuoroethane to give anti-explosive and flame-retardant properties.

Using Example 3 as a basis the composition of Example 1 is seen to evolve as the desirable commercial product. The water acts as a safety agent to prevent fogging under relatively different conditions of use and the triethanolamine prevents water marks and streaks on the finished work.

Most commercially available ethyl alcohol is denatured to insure use for technical purposes only. The denaturants may exercise unwanted effects on our drying solution. We have determined that certain denaturing substances are innocuous and thus arrive at an overall composition below.

Example 4 Mix 67 parts ethyl alcohol, 7 parts isopropyl alcohol, /2 part methyl isobutyl ketone, 13 parts trichlorotrifluoro- If it is.

ethane, parts distilled water and 2 parts triethanolamine, all by volume.

In any of these examples the order of mixing is not important. In Example 4 the first three substances comprise commercially obtainable denatured ethyl alcohol. Distilled water has been specified to prevent unwanted residual reactions with the photographic emulsion due to minerals or spoilage of the drying solution on the shelf due to bacterial growth, etc. If tap water is available with low mineral content, notably without calcium and magnesium carbonates, and the water is sterilized by boiling, such water may be used.

In the use of our drying solution the proportion of water increases therein as water is removed from the gelatin. The solution is effective over a wide range of water content but ceases to retain its useful properties for the purpose intended when this reaches 85%. At this point the trichlorotrifluoroethane separates and goes to the bottom of the container (density 1.5 grams/cubic cm.). It is not soluble in water nor is water absorbed in it; yet with the nominal amount of water present in our composition the admxture is complete without the need for supersonic homogenization or similar treatment. The separation of the trichlorotrifluoroethane serves as a convenient indicator as to when the drying solution is exhausted. We have found that the solution may be rejuvenated by treatment with known desiccants. Calcium chloride, potassium carbonate, calcium sulphate, or silica gel may be employed. Such materials should be contained in a funnel with rapid filter paper, a porous bag, or by other means by which the solution reaches the desiccants but so that the latter will not remain in the treated solution.

Our drying solution is not limited to use with motion picture film having an acetate base, but may be used with emulsions on glass, paper and other equivalents. It is non-toxic if inhaled in ordinary use, or it brought in contact with the skin. In tests, continued working with the hands in the solution each day for a few months did not give a harmful effect; rather, the general condition of the skin appeared to be completely healthy.

An increase in resistance of the film to scratching has been noted after the drying liquid has been used. This is believed due to the action of alcohol and triethanolamine in hardening the emulsion.

A self-lubricating property of film dried according to this invention appears due to the trichlorotrifluoroethane ingredient. as also the anti-oil mark effect noted in handling the film.

Having thus fully described our invention and the manner in which it is to be practiced, we claim:

1. A liquid for drying gelatin emulsions consisting of not more than 48 nor less than 8 parts of trichlorotrifiuoroethane, not more than 2 nor less than 1 parts triethanolamine, and not less than 50 nor more than 90 parts of alcohol, said alcohol being half ethyl and half isopropyl, all per 100 parts by volume.

2. A liquid for dehydrating gelatin emulsions com- Cit posed of not more than 28 nor less than 8 parts trichlorofiuoroethane, not more than nor less than 5 parts water, not more than 2 nor less than 1 parts triethanolamine and not less than nor more than 43 parts ethyl and not less than 25 nor more than 43 parts isopropyl alcohols, all per 100 parts by volume.

3. A rapid-acting flame-retardant liquid dryer for gelain layers comprised of parts ethyl alcohol, 13 parts 1,l,Z-trichlorotrifiuoroethane, 10 parts water and 2 parts triethanolamine, all per parts by volume.

4. A rapid-acting flame-retardant liquid dryer for gelatin layers comprised of 38 parts ethyl alcohol, 37 parts isopropyl alcohol, 13 parts 1,l,Z-trichlorotrifiuoroethane, 10 parts water and 2 parts triethanolamine, all per 100 parts by volume.

5. A non-toxic liquid for dehydrating gelatin layer emulsion within a time interval of one minute by displacing the water therein, which liquid is flame retardant, composed of 62 to 84 parts ethyl alcohol, 13 to 17 parts trichlorotrifiuoroethane, 8 to 10 parts distilled water and 2 parts triethanolamine, all per 100 parts by volume.

6. A liquid for dehydrating gelatin layers containing 68 parts ethyl alcohol, 7 parts isopropyl alcohol as a de naturant thereto, 13 parts l,1,Z-trichlorotrifluoroethane, 10 parts water and 2 parts triethanolamine, all per 100 parts by volume.

7. A flame-retardant liquid for desiccating gelatin layers composed of 67 parts ethyl alcohol, 7 parts isopropyl alcohol, 1 part methyl isobutyl ketone, 13 parts 1,1,2- trichlorotrifluoroethane, 10 parts water and 2 parts triethanolamine, all per 100 parts by volume.

8. A liquid for dehydrating gelatin containing 38 parts ethyl alcohol, 37 parts isopropyl alcohol, 13 parts trichlorotrifiuoroethane, 10 parts water and 2 parts triethanolamine, per 100 parts by volume, in which in use gravity separation of the trichlorotrifiuoroethane to the bottom of the container indicates exhaustion of the dehydrating properties of the liquid.

9. A non-toxic liquid dryer for photographic gelatin emulsions acting to dry the same by displacement of water therein contained within a period of one minute having flame-retardant and non-fogging characteristics composed of the mixture; 67 parts ethyl alcohol, 7 /2 parts isopropyl alcohol, /2 part methyl isobutyl ketone, 13 parts 1,l,Z-trichlorotrifluoroethane, 10 parts distilled water and 2 parts triethanolamine, all by per 100 parts by volume.

References Cited in the file of this patent UNITED STATES PATENTS 2,377,325 Crabtree et al. June 5, 1945 2,742,321 Mina et al Apr. 17, 1956 FOREIGN PATENTS 59,548 Argentina Aug. 16, 1947 OTHER REFERENCES Camera, September 1956, vol. 35, #9, page 432. 

1. A LIQUID FOR DRYING GELATIN EMULSIONS CONSISTING OF NOT MORE THAN 48 NOR LESS THAN 8 PARTS OF TRICHLOROTRIFLUOROETHANE, NOT MORE THAN 2 NOR LESS THAN 1 PART TRIETHANOLAMINE, AND NOT LESS THAN 50 NOR MORE THAN 90 PARTS OF ALCOHOL, SAID ALCOHOL BEING HALF ETHYL AND HALF ISOPROPYL, ALL PER 100 PARTS BY VOLUME. 